Indicators of the type disclosed are known to include metallic body with a threaded attachment shank having a pressure fluid passage adapted for connection to a source of vacuum or pressure to be measured. A cylindrical bore is provided within the body which communicates with the passage and has a threaded open end receiving an end plug having a bore and which is threaded into the body. A piston is nested in the cylinder and has a piston rod axially extending through the cylinder bore and through the plug. A compression spring is interposed between the plug and piston retainingly engaging the piston and the piston being variably movable longitudinally against the spring on application of fluid under pressure, with the extent of movement providing a visual indication of the pressure or vacuum applied. Examples of this type of indicator are shown in U.S. Pat. No. 3,677,089 to Clyde J. Martin, granted July 18, 1972 and U.S. Pat. No. 3,910,210 of Clyde J. Martin, granted Oct. 7, 1975.